Ball valves as presently known present a number of advantages over other types of valves. Ball valves permit immediate flow or shut-off with a quarter turn of a handle associated with the ball. Such ball valves are leak tight, do not require lubrication, and ball seating rings within the valve housing can be easily and quickly replaced. The ball member per se is also easily replaced. Ball valve constructions utilize a small number and simple design of parts which constitute the valve, and such valves are relatively inexpensive and easily manufactured.
When employed in equipment where even a small amount of contamination of the material flowing through the valve cannot be tolerated, ball valves present a disadvantage. Situations especially in the production of pharmaceuticals, parenteral solutions and foodstuffs are especially significant as regards elimination of such contamination. The contamination in ball valves normally occurs in that the space surrounding the ball inside the housing fills with fluid when the ball is rotated in order to effect a closed or an open position. As the valve is opened from a closed position, a small portion of this trapped fluid leaves the space to exit from the valve while at the same time an equal small portion of piped fluid enters this space from the incoming side of the valve. It has been found that the bulk of this trapped fluid remains in this space between the ball and the housing and cannot be entirely removed unless the valve is completely disassembled. This entrapped fluid can contaminate subsequent batches of a solution with substances which were in a previously piped solution if the valve is operated when the subsequent batches pass through it. Microorganisms and pyrogens which can develop in this entrapped fluid cannot be removed in a normal flushing operation and these can also contaminate solutions subsequently valved.
It is this possible or inherent contamination possibility that the present invention is designed to eliminate. Some previous ball valve structures have incorporated features which might be considered as broadly analogous to the solution presented by the present ball valve. The ball in standard two-way ball valves is provided with a wide axial flow bore. The drawback as referred to above, broadly speaking, is eliminated in the present invention by providing a ball in which a portion of the ball body is removed to provide communication between the bore and the space surrounding the ball. The present ball when utilized in a two-way ball valve provides a self-flushing feature to eliminate this contamination problem. The present structure is different from anything known in the prior art.
U.S. Pat. No. 3,148,693 discloses a ball which must have two trunnions secured to the side surfaces of the ball so that the ball can be pulled up by hooks against a ball seat. The sealing surface in this ball faces the direction of flow and there is a greater likelihood that leaks will develop when higher fluid pressures are experienced. to minimize this situation a screw threaded collar must be utilized and screwed up more tightly and this results in increased wear on the seating ring. The present ball eliminates the necessity for the trunnions and is not pulled in any one direction but merely "floats" between two seating rings so that minimal wear on the seating rings occurs. Additionally the seating surface of the present ball is away from the direction of flow and the pressure of the fluid in effect forces the ball against the seating ring on the outflow side, in the closed position of the valve. This ensures a better sealing contact being made between the ball and the seating ring.
U.S. Pat. No. 3,333,813 discloses a ball having an opening adapted to permit fluid to flow from a central channel into a valve housing space but is entirely inadequate to provide self-flushing or flow of fluid into and from this housing space. The purpose of this channel is merely to allow fluid to enter the space in the housing to equalize the pressure against the seating rings. The valve structure of this patent also utilizes two trunnions in order to maintain the ball in a stable position within the housing.
The present invention only now provides a ball valve construction which does not allow formation of contaminated dead spaces and results in outstanding advantages to processer of, for example, pharmaceuticals, food and beverages.